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Gizmo 14th May, 2004 11:03 PM

RAM Voltages

Originally Posted by EPoX Tech
Anyone else had any luck VModding a 9800Pro to get past 500 core clock ? I've been trawling the web to try to get some other numbers.

Memory is devilish to try to vmod and get any further - been to 3.6v VDD and 1.8v Vref with increased and decreased VDDQ and still have difficulty getting past 390Mhz - really have tweaked the envelope and not found a way with this original ATi card with Samsung BGA 3.3's to go that extra mile.

This brings up something that I am curious about, ET. Maybe you can shed some light on it. The last time I got dirty with RAM, 30-pin SIMMs were state-of-the-art.

I understand that modern DDR SDRAM uses VDD for it's internal operation, VDDQ for the I/O buffers, and VREF for the reference voltage for the high/low transitions of the I/O signals. Virtually every implementation that I have looked at closely simply ties the VDD and VDDQ voltages together and sets VREF to 1/2 of VDDQ.

Is there any benefit to separating these two? Seems like one could gain some improvement in signal integrity (and thus transmission speed) by increasing the I/O buffer voltage while leaving the core voltage alone without unduly stressing the RAM....

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